There is interest in producing passenger vehicles driven by an electric motor powered by a re-chargeable battery (for example, a lithium-ion battery). The operating range of the battery powered vehicle would be increased using an on-board electric generator driven, upon demand, by a gasoline engine. For relatively short driving excursions, the capacity of the battery would suffice and the gasoline engine would not be started. At the completion of such trips the battery would be recharged from a 110 volt AC source. Such a vehicle is sometimes called a plug-in hybrid vehicle.
Since many local driving trips could be completed within the electrical power capacity of the battery it is anticipated that many days could pass without starting the gasoline engine. But the engine would be necessary when longer trips are taken. By way of example, it is contemplated that battery-only trips (before plug-in recharging) may be of up to about forty miles. But the gasoline engine-driven electric generator would be used to increase the range of the vehicle to several hundred miles.
Despite its intermittent usage the plug-in hybrid gasoline engine will, of course, require on-board fuel storage. Gasoline stored in a vehicle fuel tank is exposed to ambient heating which increases the vapor pressure of the volatile hydrocarbon fuel. In conventional gasoline powered engines fuel tank vapor (typically comprising lower molecular weight hydrocarbons) is vented to a canister containing high surface area carbon granules for temporary adsorption of fuel tank emissions. Later, during engine operation ambient air is drawn through the carbon granule bed to purge adsorbed fuel from the surfaces of the carbon particles and carry the removed fuel into the air induction system of the vehicle engine. As stated, such plug-in hybrid vehicles operate mostly on batteries which are charged during the night by plugging into home AC outlets. A plug-in hybrid vehicle IC engine may not run for several days which results in no purging (cleaning) of the evaporative emission control canister. However, a conventional fuel tank will be generating diurnal vapors everyday. It would be desirable to use the familiar canisters but the mode of their operation must be altered to contain fuel vapor tending to flow from the fuel tank. This invention makes use of a familiar fuel evaporative emission control canister in a method of operation adapted for a plug-in hybrid type vehicle.